Ink introducing tube and writing instrument incorporated with the same

Abstract

Provided is an ink introducing tube which realizes a stabilized ink supply from an ink tank located at the rear portion of a felt pen into a tip at the front end thereof, and a writing instrument incorporating it. On the inner peripheral wall of an ink introducing tube through which an ink tank is communicated with a tip located at the front end, a plurality of protrusions are formed to provide therebetween a passage for downward flow which utilizes the capillary action of the protrusions, and the interior space of the ink introducing tube which is surrounded by the tips of the plural protrusions is formed as a large space so that the capillary action can take place. Thus, the flow of air to the ink tank moves upwardly through the interior space while changing into air foam during the ascent, whereas the ink flows downward while being retained between the protrusions. Therefore, replacement of the ink by the air can be performed smoothly whereby ink blobbing is prevented and flawless writing is realized.

What is claimed is:  
     
       1. An ink introducing tube for introducing ink from an ink tank of a closed writing instrument into a writing tip characterized in that the ink introducing tube comprises a plurality of protrusions formed from the inner peripheral surface of the tube toward the center so as to exert strong capillary action and extended in the axial direction, and intervals between the plurality of protrusions being set to approximately 10 to 100 microns, and a central space surrounded by the free ends of the plurality of protrusions, and has transverse distances therein set to approximately 100 to 1000 microns that would make the capillary action difficult to take place in the central space, over the entire length of the ink introducing tube. 
     
     
       2. An ink introducing tube for introducing ink from an ink tank of a close writing instrument into a writing tip as claimed in  claim 1 , wherein the transverse distance of the central space are set to approximately 300 to 500 microns. 
     
     
       3. A writing instrument, comprising an ink tank provided inside a writing instrument shaft, a writing tip located at a forward end of the writing instrument shaft, an ink introducing tube, provided with connections between the ink tank and the writing tip in the writing instrument shaft, which has axially extended portions with strong capillary action surface formed longitudinally along an inner peripheral surface of the ink introducing tube and a cylindrical spaces, surrounded by free ends of the plurality of protrusions formed in a central portion of the ink introducing tube, that would make the capillary action difficult to take place with cylindrical space, and an inner wick having the capillary action for surrounding a periphery of the portion where the ink introducing tube and the writing tip are connected. 
     
     
       4. A writing instrument as claimed in  claim 3 , wherein a periphery of the portion where the ink tank and the ink introducing tube are connected, is provided with an air reservoir. 
     
     
       5. A writing instrument as claimed in  claim 3 , wherein the transverse distances of the central space is set to approximately 300 to 500 microns.